1. Field of the Invention
This invention relates to a selectively damped travelling wave tube having a periodically alternating magnetic field for guiding the electron beam and comprising a delay line consisting of cells which are separated from each other by partitions and which are positioned one behind the other in the direction of the beam, wherein at least one chamber resonator is provided with damping material and coupled to at least one of the cells, the resonant frequency of the chamber resonator being at least almost equivalent to a predetermined interference frequency.
2. Description of the Prior Art
In general, such a travelling wave tube is known from the German Letters Patent 1,297,768. Embodiments of travelling wave tubes are disclosed in this publication in which chamber resonators are inserted into non-magnetic spacers which are arranged between adjacent partitions. The spacers are shaped like rings which are provided with tongues and are encased by the guide magnet of the tube. With this resonator arrangement, in particular with delay lines having a periodically alternating guide field, additional radial asymmetries or weakings, respectively, of the axial field strength occur which are known to be able to greatly impair beam guidance. If it is desired to adjust the asymmetry by means of maintaining a constant outer diameter at the spacers, an increase of the transverse dimensions and of the weight of the tube will simultaneously be required and, in addition, if the same magnetic power is applied, an altogether weakened guide field will result, even though it is radially symmetrical.